Khalifa University’s Prof. Lourdes Vega was invited to serve as a guest Editor of a special issue of Industrial and Engineering Chemistry Research from the American Chemical Society dedicated to the latest technological developments and innovations that underpin the establishment of a hydrogen economy.
A continued reliance on fossil fuels for energy production is not sustainable, particularly as energy demand continues to rise in parallel to the industrialization of developing countries and world population growth. Not only does reliance on the combustion of fossil fuels result in greenhouse gas emissions detrimental to the environment, it also creates energy security challenges given that oil, coal, and natural gas are geographically concentrated and subject to volatile prices.
As the world seeks more efficient and environmentally-friendly sources of energy, attention has turned to low-carbon hydrogen production and applications. Hydrogen offers a potential decarbonization solution but technical and economic factors stand in its way.
Given this topic’s global relevance, Industrial and Engineering Chemistry Research dedicated a special issue to hydrogen and asked two recognized experts from the editorial board to act as guest editors. Prof. Lourdes Vega, Director of the Khalifa University Research and Innovation Center on CO2 and Hydrogen (RICH) and Acting Senior Director of the Petroleum Institute, and Prof. Sandra Kentish, University of Melbourne, were selected and invited to edit this special edition, which included three papers from RICH researchers.
“Governments internationally are reacting to global warming wake-up calls, putting forward new targets and timeframes for decarbonizing industries and societies,” Prof. Vega said. “To achieve these objectives, the policies of most developed countries now include a commitment to hydrogen as a key alternative energy source.”
Hydrogen fuel is a zero-carbon fuel that can be used in fuel cells or internal combustion engines, including buses, passenger cars, and spacecraft. Hydrogen is abundant in enormous quantities on Earth, but not freely. It is bound in water, hydrocarbons, and other organic matter, making efficient extraction of hydrogen one of the main challenges to using it, or one if it’s derivatives, as a fuel or feedstock for other applications.
Hydrogen production is usually classed in terms of color labels: ‘grey’ hydrogen, the most common way of producing hydrogen today, is obtained from methane and water in what it is called steam methane reforming, producing a large amount of CO2 emitted to the atmosphere; ‘blue’ hydrogen is produced through the same process, but adding a subsequent process in which CO2 is captured via carbon capture technologies for further utilization or storage; and ‘green’ hydrogen is produced entirely from renewable energy sources used to split water or, via a much less common approach, hydrogen sulfide.
Osahon Osasuyi, Dr. Georgia Basina, Dr. Yasser Al Wahedi, Dr. Mohammad Abu Zahra, Dr. Giovanni Palmisano, and Dr. Khalid Al-Ali, all from KU’s Department of Chemical Engineering and members of the RICH Center, investigate the production both hydrogen and sulfur from hydrogen sulfide, a toxic byproduct of the oil and gas industry. While many studies have examined the potential of the process experimentally, there is a lack of comprehensive research into how to select the appropriate metal for the thermochemical splitting process. In this paper, 17 metals were shortlisted, with six found to be promising candidates with high efficiency and high hydrogen yield.
Once produced, hydrogen can be used in many of the same applications as natural gas, except it produces no carbon or methane emissions when combusted.
“Hydrogen can help to decarbonize the economy and to reach a net zero emissions goal in a variety of ways,” Prof. Vega said. “In addition to providing a viable solution for energy storage from intermittent renewable energy, hydrogen is also seen as a key source of combined heat and power to replace natural gas and for transport, particularly in difficult to abate sectors such as heavy vehicles, trains, and shipping, since it can offer a zero-emission alternative to fossil fuels.”
“However, there is clearly a long way to go before any country can claim to be a hydrogen economy. Making this energy transition is not an easy task for any nation. The price of renewable energy must decrease to make green hydrogen competitive; new distribution networks, refueling stations and transport pathways must be developed to carry hydrogen to the final destination; and equipment and infrastructure must be adapted. These changes are not straightforward.”
Once hydrogen has been produced, it needs to be stored and transported. Hydrogen has extremely low volumetric energy density, meaning effective hydrogen storage must usually be done at very high pressures or low temperatures to reduce the volume. Unfortunately, compression for storage or transport can consume 20 percent of the energy of the hydrogen itself.
KU’s Dr. Anish Varghese, Dr. Suresh Kumar Reddy, and Dr. Georgios Karanikolos, from the RICH Center and the Department of Chemical Engineering, looked at storing hydrogen using solid materials, including metal-organic frameworks, which are porous and easily tunable to adsorb hydrogen for storage. The team developed a metal-organic framework using copper and graphene oxide for hydrogen storage at ambient temperature, which could be more practical compared to traditional cryogenic conditions.
For hydrogen transport, leakage from infrastructure through valves and other fittings is a significant safety and economic concern. Hydrogen is an extremely small molecule, which means it is difficult to retain, and it also readily forms atomic radicals when in contact with steel and other metals, which puts infrastructure at risk of embrittlement and ultimately, failure. One option is to blend hydrogen into existing natural gas networks as studies suggest these pipelines can handle a blend of up to 30 percent hydrogen before embrittlement becomes a concern.
KU’s Dr. Ismail Alkhatib, Dr. Ahmed AlHajaj, Prof. Ali Almansoori and Prof. Vega, all Department of Chemical Engineering, explore the changes in pipeline thermodynamics that might occur when a blend is used. Despite the attractiveness of hydrogen blending, it’s important to know just how much hydrogen can be included in natural gas pipelines without jeopardizing the safety and operation of the existing pipeline grid. The team also quantifies the effect of hydrogen concentration in the properties of natural gas, with changes noted in the density and speed of sound in particular. This knowledge will help not only for transportation, but also for the utilization of hydrogen blends to replace natural gas, as a way of decarbonizing the industry.
“We hope that readers find these articles of interest,” Prof. Vega said. “Only through the concerted effort of many scientists and engineers can we drive the hydrogen economy further and advance action against climate change.”
24 May 2022